1. Field of the Invention
The present invention relates to an injection molding apparatus and, in particular, to a manifold plug for use in a manifold.
2. Related Art
Manifolds for injection molding systems often include manifold plugs for changing direction of the melt flowing through manifold melt channel, for example, turning the melt channel towards a hot runner nozzle. Manifold plugs are utilized because it is more cost effective to drill out a section of a manifold in which to insert the manifold plug than it is to drill a melt channel including turns directly into the manifold.
Injection molding systems using valve gating often include a valve pin bushing bridging the air gap between the manifold and the back plate in order to guide the valve pin and prevent leakage of melt from the manifold. A valve pin bushing is shown, for example, in U.S. Pat. No. 4,740,151 to Schmidt et al. The Schmidt et al. patent shows a separate manifold plug and a nozzle bolted to the manifold. Utilization of separate pieces to perform the functions of guiding the valve pin, changing direction of the manifold melt channel, and connecting the nozzle to the manifold requires very tight tolerances. Variations in expansion rates and movement during heating can cause such multiple parts to become misaligned, resulting in leakage. Further, having such multiple parts requires a larger inventory.